Promissory Note

A promissory note is a signed written promise to pay a set sum to a named party, on stated terms. In a mortgage loan the note is the debt itself: it records the amount, rate, term, payment schedule and any prepayment penalty on a DSCR loan.

The note and the security instrument are separate documents. The note is the promise to pay. The mortgage or deed of trust is what lets the lender take the property if the promise is broken.

For DSCR purposes the note fixes the numbers in the denominator. Its rate and amortization produce the principal and interest payment, and any interest-only period or adjustable-rate terms written into it change that payment, and the ratio, over time.

Further reading: Promissory Note on Wikipedia.